The incidence of lung cancer in the United States is currently over 100,000 new cases per year and is expected to rise to nearly 300,000 by the year 2000. G. Gori and J. Peters, Prev. Med. 4:239-246 (1975). This expected increase is related both to the continued use of cigarettes and to exposure to various pollutants that exist in the work place and in urban home environments. More than two-thirds of the cases of bronchogenic carcinoma afflict middle-aged men, but the incidence among women is rising, and the proportion of female patients is expected to rise at an even greater rate as the effects of women's having entered the work place and begun smoking in increased numbers years ago are seen. The incidence today of lung cancer is 4-10 times greater in moderate cigarette smokers than in nonsmokers, and is 15-30 times greater in heavy smokers than in nonsmokers. The rising incidence is particularly alarming in view of the latent nature of this disease since the effect of exposure to a variety of substances found in industrial environments, such as asbestos, are just beginning to be seen.
Despite considerable efforts at early diagnosis and treatment, survival rates for bronchogenic carcinoma remain low. Although prognosis depends not only on cell type but also on the stage at which the disease is detected, the overall survival rate is still only about 10-25%. Recently, efforts have been made to more closely survey those individuals who fall into defined high-risk groups, such as those who smoke heavily or who are or have been chronically exposed to known carcinogens. Thus far, the most promising approach has been the screening of males of 45 years of age or older who have smoked at least 2 packs of cigarettes a day for 20 years. A combination of chest x-ray and pooled sputum analysis every four months has indicated lung cancers at an early stage of the disease, yielding a more favorable prognosis. More invasive methods of detecting the disease have been made, such as the use of fiber optic bronchoscopy, but these approaches have not significantly affected the rate of early diagnosis, which is still thought to be one of the most important considerations to long-term survival or ultimate cure.
The detection of other disease states by non-invasive methods has, so far, out-paced the use of such methods to detect lung cancer. Lung air, breath, and saliva are, for example, easily obtainable physiological samples that contain an array of volatile constituents whose presence has provided evidence of other systemic disease conditions or infection. The chemical identity of many volatile constituents, as well as their use in the study and diagnosis of diabetes, respiratory virile infection, and renal insufficiency has been described. A. Zlatkis, R. Brazell and C. Poole, Clin. Chem., 27:789-797 (1981). Analysis of respiratory air by gas chromatography/mass spectrometry has shown the presence of simple endogenous alcohols, ketones, amines and numerous compounds of exogenous origin. B. Krotoszyinski, G. Gabriel and H. J. O'Neill, Chrom. Sci. 15:239 (1977). In several disease conditions, for example, specific volatile metabolites have been identified in breath samples, having been transferred into the aveolar air space from the blood. An example is the elevated levels of mercaptans and lower aliphatic acids found in the breath of patients with cirrhosis of the liver. S. Chen, V. Mahadevan and L. Zieve, J. Lab. Clin. Med, 75:622-27 (1970).
Monitoring the quantitative change in the presence of known indicators of disease or infection, over time, can indicate changes in physiological state, reflecting the advancement of the disease or the effect of treatment. For example, the classic uremic breath odor denotes the presence of dimethylamine and trimethylamine. M. Simenhoff, J. Burke, J. Saukkonen, A. Ordinario and R. Doty, New England J. Med., 297:132-135 (1977) Gas chromatography/mass spectrometry analysis of breath volatiles, however, shows a marked reduction in the concentration of these amines following hemodialysis, demonstrating the relationship between lung air and blood for small organics and the use of sampling lung air to monitor treatment efficacy.
The detection of various other pathological states through the analysis of volatiles given off by various body samples is documented. High concentrations of acetone in breath samples of diabetics has been found. A. Zlatkis, R. Brazell and C. Poole, Clin. Chem., 27:789-797 (1977). It has also been speculated that bacterial infections of the lung could be a further source of indicative volatiles present in expired lung air. B. Lorber, Amer. Rev. Respiratory Dis., 112:875-877 (1975). U.S. Pat. No. 4,349,626 (issued Sept. 14, 1982, to Labows et al) discloses a method of detecting the presence of Pseudomonas aeruginosa through the analysis of characteristic volatile metabolites, such as various ketones and/or sulfur metabolites, associated with this infection. The disclosed detection method involves analyzing the volatiles in a head space over a sample of material associated with the site of the suspected infection, such as skin, sputum, breath, or saliva. U.S. Pat. No. 4,334,540 (issued June 15, 1982 to Preti et al) discloses a method of diagnosing periodontal disease through the detection of pyridine compounds in the headspace over, for example, breath or saliva samples.
The application of gas chromatography analysis techniques to the identification of unknown microorganisms is well known in general, and as described above, has been used in detection of various organic metabolites. See Zechman and Labows, "Volatiles of Pseudomonas aeruginosa and Related Species by Automated Headspace Concentration - Gas Chromatography," Can. J. Microbiol 31:232-237 (1985). The techniques which have been developed are based on analysis of either the unique metabolites of a given organism or on its individual structural components. Culture extracts have, for example, revealed specific amines for Clostridia (Brooks et al), "Further Studies on the Differentiation of Clostridium sordelli from Clostridium bifermentans by Gas Chromatography", Can. J. Microbiol., 16:1071-8 (1970). Specific hydroxy acids and fatty acids have been identified for Neisseria. Brooks et al, "Analysis by Gas Chromatography of Hydroxy Acids Produced by Several Species of Neisseria", Can. J. Microbiol. 18:157-168 (1972); Brooks et al, "Analysis by Gas Chromatography of Fatty Acids Found in Whole Cultural Extracts of Neisseria Species", Can. J. Microbiol. 17:531-541 (1970). As mentioned above, bacteria cell wall preparations have been examined for unique fatty acid profiles, including such profiles for Pseudomonads. C. W. Moss, S. D. Dees, "Cellular Fatty Acid and Metabolic Products of Psuedomonas Species Obtained from Clincal Specimens", J. Clin. Microbio., 4:492-502 (1976); and T. J. Wade, R. J. Mandel, "New Gas Chromatographic Characterization Procedure: Preliminary Studies on Some Pseudomonas Species", Applied Microbio., 27:303-311, (Feb. 1974). Pyrolysis-gas chromatography of whole cell Clostridia bacteria has also been reported as giving identifiable differences in the observed fragmentation patterns. Reiner, et al, "Botulism: A Pyrolysis-Gas-Liquid Chromatographic Study", J. Chromatogr. Sci. 16:623-629 (1978).
Headspace analysis has also been applied to samples of human body fluids including saliva, urine, and blood serum. For references on this topic, please refer to Kostelc, et al, "Salivary Volatiles as Indicators of Periodontitis", J. Periodont. Res., 18:185-192 (1980); Matsumota, et al, "Identification of Volatile Compounds in Human Urine", J. Chromatogr., 85:31-34 (1973); Zlatkis, et al, "Concentration and Analysis of Volatile Urinary Metabolites", J. Chromatogr. Sci., 11:299-302 (1973); Liebich, et al, "Volatile Substances in Blood Serum: Profile Analysis and Quantitative Determination", J. Chromatogr., 142:505-516 (1977).
There remains a need for a non-invasive method for detecting the presence of lung cancer at an early stage, a method which, unlike the conventional invasive procedure, people will not be reluctant to undergo and which will thereby enhance early detection.